The manufacture of semiconductor wafers typically involves a series of processes for the blanket and selective deposition of a plurality of layers of material on a substrate, for the patterning and etching of the deposited layers, and for other treatment. The purposes of each of the various layers on the wafer are the fulfilled as a result of the locations or patterns of the film material on the wafer and as a result of the properties of the materials of which the layers are made.
For example, some films are deposited for their conductivity and are used for carrying current in the semiconductor devices or circuits formed on the wafer. Other films are deposited for their insulative properties or for the wide variety of semiconductor properties on which device characteristics depend. Still other films are employed as boundary layers between two other layers, serving as diffusion barriers to control the migration of material from one layer into another. The properties that the films possess depend not only on the composition of the material of which the film is formed but on physical and other characteristics of the film, which may vary with the conditions under which the film is deposited.
Titanium nitride (TIN), for example, is capable of providing properties that give it a variety of important uses. Important among these uses is that of a diffusion barrier in VLSI metallization technology. The properties that make titanium nitride films desirable for use as diffusion barriers in microelectronic devices are its relative inertness, its high melting point, its thermal Stability, its low resistivity and its resistance to alloying with aluminum at temperatures of up to 500.degree. C.
Polycrystaline TiN films are deposited by a variety of techniques, including reactive DC and RF magnetron sputtering, ion plating, activated reactive evaporation, and chemical vapor deposition (CVD). Each technique, depending on the processing parameters, can produce a TiN film with different physical properties. For example, variation in resistivities from 25 to 4500 .mu..OMEGA. cm and crystal orientations of &lt;111&gt; and &lt;200&gt;, in various proportions, may result. Generally, properties of interest in the use of TiN films for semiconductor diffusion barriers are uniformity, resistivity, stress and crystal orientation. Many of the properties desired are those that are related to, or in part a function of, crystal orientation.
The correlation between the resulting properties of a deposited film and the process parameters that produce the film are capable of being determined by experimentation. The production of films with certain desired properties by controlling the process parameters is sometimes achievable in a laboratory setting with varying degrees of difficulty. Absent from the art of semiconductor manufacture, however, are methods and equipment that produce semiconductor wafers on a commercial scale having films of which the most desired properties, particularly properties related to film Crystal orientation, can be controlled.
Accordingly, there is a need for a method and apparatus for controlling the properties of deposited thin films on semiconductor wafers, particularly for controlling resistivity, stress, diffusion barrier effectiveness, as well as crystal orientation per se and other properties dependent thereon, for titanium nitride and films which also possess the properties described herein.